With the development of semiconductor technology, display devices tend to have a large size in order to satisfy the consumers' demand. As a display device becomes large, the load of a display panel, for example, a liquid crystal display (LCD) panel, increases. Source lines or data lines in the display panel are driven by a data (or source) driver device.
When a display device, for example, an LCD television (TV), becomes large, a load resistor, for example, a source line resistor, of a display panel, for example, an LCD panel, is manufactured with a decreased value in order to reduce power consumption of the display panel. On the other hand, when the display device becomes large, the load capacitance, for example, source line capacitance, of the display panel is increased.
When the value of the load resistor of the display panel is decreased and the load capacitance of the display panel is increased, the power consumed in the data driver device to drive the source lines of the display panel increases, causing a considerable amount of heat to be generated in the data driver device. More specifically, power consumption increases significantly in charge-share switches included in an output circuit of the data driver device.
FIG. 1 illustrates an output circuit 100 of a conventional data driver device. Referring to FIG. 1, the output circuit 100 includes a plurality of output terminals 111 through 11n. The output terminals 111 through 11n respectively receive gray voltages V1 through Vn and output them to source lines S1 through Sn, respectively of a display panel (not shown) to respectively drive the source lines S1 through Sn.
Each of the output terminals 111 through 11n includes a respective amplifier 121 through 12n, a data line switch T1 through Tn, a charge-share switch H1 through Hn, and an output pad PAD1 through PADn. Each of amplifiers 121 through 12n respectively included in the output terminals 111 through 11n amplifies a corresponding gray voltage V1 through Vn output from a digital-to-analog converter (DAC) (not shown) is of the data driver device and outputs the respective amplified gray voltage V1 through Vn. When the data driver device drives source lines in the display panel using a dot inversion method or a source line inversion method, an odd numbered gray voltage, for example, V1, and an even numbered gray voltage, for example, V2 which are adjacent each other among the gray voltages V1 through Vn, have opposite polarities.
The first data line switch T1 of the first output terminal 111 is switched in response to a first control signal P1 and a first inversion control signal PB1, so that an output of the first amplifier 121 is transmitted to the first source line S1 of the display panel via the first output pad PAD1. Charge-share switches H1 through Hn are connected between a share line Sh and data line switches T1 through Tn, respectively. The charge-share switches H1 through Hn are switched in response to a second control signal P2 and a second inversion control signal PB2. When the data line switches T1 through Tn are turned off the charge-share switches H1 through Hn are turned on.
When the charge-share switches H1 through Hn are turned on, the source lines S1 through Sn in the display panel are connected with one another via the share line Sh, so that charges are distributed to a plurality of cells in the display panel. As a result, the source lines S1 through Sn share a source line voltage, that is, a charge-share voltage after the completion of the charge distribution. At this time, the share line Sh has the charge-share voltage.
FIG. 2 illustrates a pair of the adjacent output terminals, such as 111 and 112 illustrated in FIG. 1, and loads LOAD1 and LOAD2 respectively corresponding to the adjacent output terminals 111 and 112 in a display panel (not shown). Only one pair of the output terminals, such as 111 and 112, are illustrated in order to clearly describe power consumed by charge-share switches, for example, H1 and H2, of the data driver device when the display panel is charge shared. Each of the loads LOAD1 and LOAD2 is modeled of the resistance and capacitance of each of the source lines S1 and S2.
Referring to FIG. 2, when the display panel is charge shared, the data line switches T1 and T2 are turned off and the charge-share switches H1 and H2 are turned on. When the first gray voltage V1 is a positive voltage and the second gray voltage V2 is a negative voltage, a voltage of the first source line S1 is greater than that of the second source line S2. Accordingly, when the display panel is charge shared, a share current Is flows from the first source line S1 to the second source line S2 via the charge-share switches H1 and H2, as illustrated in FIG. 2. For the share current Is illustrated in FIG. 2, only the charge-share between the first source line S1 and the second source line S2 has been considered. When all of the source lines S1 through Sn in the display panel are considered, the share current Is may have a different value.
When a load resistance of a source line in a display panel decreases and a load capacitance of the source line increases, power consumption due to a share current in charge-share switches increases considerably. As a result, heat generation in a data driver device may also be increased. Accordingly, it is desired to reduce power consumed in the charge-share switches in an output circuit of the data driver device when the source lines in the display panel are charge shared.